AudioCalcs
Audio Power Calculator — Voltage, Impedance & Watts
Calculate power from voltage and impedance, or voltage from power and impedance.
How We Calculate This
Power from voltage and impedance
P = V² / R
Voltage from power and impedance
V = √(P × R)
dBW and dBm
dBW = 10 × log10(P) where P is in watts
dBm = 10 × log10(P × 1000) where P is in watts
Frequently Asked Questions
Power = Voltage² / Impedance (P = V²/R). Doubling the voltage quadruples the power. Halving the impedance doubles the power at the same voltage. This is why a 4-ohm speaker draws roughly twice the power of an 8-ohm speaker from the same amplifier.
RMS (root mean square) power is the continuous power that a speaker or amplifier can handle. Peak power is the instantaneous maximum — typically 2× the RMS value for a sine wave. Always use RMS power for meaningful comparisons.
dBW expresses power relative to 1 watt. 0 dBW = 1 W, 10 dBW = 10 W, 20 dBW = 100 W, 30 dBW = 1000 W. Each 3 dB increase represents a doubling of power.
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Last updated: February 2026
All calculations are estimates based on standard formulas. Always verify results for critical applications.